mash: Move TrayTracing to //ash/common/system/chromeos

ash/common/system/chromeos/tray_tracing.h

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#ifndef ASH_SYSTEM_TRAY_TRACING_H_
-#define ASH_SYSTEM_TRAY_TRACING_H_
+#ifndef ASH_COMMON_SYSTEM_CHROMEOS_TRAY_TRACING_H_
+#define ASH_COMMON_SYSTEM_CHROMEOS_TRAY_TRACING_H_
 
 #include "ash/ash_export.h"
 #include "ash/common/system/tray/tray_image_item.h"
 #include "base/macros.h"
 
 namespace views {
 class View;
 }
 
 namespace ash {
 
 class ASH_EXPORT TracingObserver {
  public:
   virtual ~TracingObserver() {}
 
   // Notifies when tracing mode changes.
   virtual void OnTracingModeChanged(bool value) = 0;

[msw, 2016/06/24 02:07:11]

nit: bonus points for clarifying silly bool param "value" or the comment.

[James Cook, 2016/06/24 16:28:17]

"Notified when |value| gets a new value which is valuable." j/k. Changed to
"enabled" here and elsewhere and clarified comment.

 };
 
 // This is the item that displays when users enable performance tracing at
 // chrome://slow.  It alerts them that this mode is running, and provides an
 // easy way to open the page to disable it.
 class TrayTracing : public TrayImageItem,
                     public TracingObserver {
  public:
   explicit TrayTracing(SystemTray* system_tray);
   ~TrayTracing() override;
@@ skipping 11 matching lines @@
   // Overridden from TracingObserver.
   void OnTracingModeChanged(bool value) override;
 
   views::View* default_;
 
   DISALLOW_COPY_AND_ASSIGN(TrayTracing);
 };
 
 }  // namespace ash
 
-#endif  // ASH_SYSTEM_TRAY_TRACING_H_
+#endif  // ASH_COMMON_SYSTEM_CHROMEOS_TRAY_TRACING_H_